Process for the manufacture of coke



June 27, 1933. K. J. SMITH Er AL 1,915,026

PROCESS FOR THE MANUFACTURE OF COKE Filed Feb. 7, 1930 Patented June 27, 1933 UNITED STATES PATENT OFFICE :KENNETH J'. SMITH AND HOWARDI V. SMITH, OF EL DORADO, KANSAS, .ASSIGNORS TO SKELLY OIL COMPANY, OF EL DORADO, KANSAS, A CORPORATION 0F DELAWARE PROCESS FOR. THE MANUFACTURE 01? COKE Application filed February 7, 1930. Serial No. 426,619.

Our invention consists in new and useful improvements in a process for the economical manufacture of coke from fuel oil and other petroleum rcsiduums. V

As practical operators in the petroleum refining industry for many years, We are aware of the fact that the manufacture of coke from fuel oil and petroleum residuums is very old. We are also well acquainted with and have practiced the manufacture of coke from fuel oils and petroleum residuums by means of shell stills and the commonly practiced method of producing coke in connection with oil cracking processes where the material being cracked is passed through a lone heated coil to a large receptacle maintained under high pressure in order to arrive at the high temperature necessary to effect cracking of the oil in the receptacle, the coke produced as a rcsult of said operation, being a by-product.

Furthermore, we are familiar with and for some time have practiced on a large scale the process of manufacturing synthetic coal, announced at the lVorlds Coal Conference in Pittsburgh in 1928, and described and illustratcd in many technical journals shortly thereafter. In this last named process the fuel oil or petroleum residuum is heated in a long coil from whence it is partially cooled and led to an open space where it is permitted to congeal into an amorphous solid comparable in many ways to bituminous coal.

The process most extensively used heretofore in the production of coke from fuel oils and petroleum residuums, as before stated, has involved the use of shell stills which for obvious reasons has been found to be a costly procedure both in time and apparatus involved. In the shell still operation a still is charged with several hundred barrels of fuel oil and heated externally to a very high temperature, until all of the volatile constituents are driven off and an incidental amount of cracking occurs, after which the coke is removed manually from the still. In such operation the coke collecting in the bottom of the still forms an increasingly thick insulation, thereby necessitating an extremely high temperature in order to penetrate and vaporize the liquid content of the still, which in a short time obviously caused burning out of the bottom of the still and necessitated repairs during which the apparatus is shut dpivn, causing a loss of time, money and materia It is the object of our invention to overcome the disadvantages of the coking processes heretofore known, our process differing radically from any of the above in the principles applied as wcll as in procedure.

The fundamental factor of our process resides in passing the material to be treated through a pipe still and impounding sutlicient tlieat in-said material, so that, atthe point of discharge from said pipe still there will be a substantially com lete vaporization of the volatile content wit rout the addition of further external heat.

The main difference between our improved process and those heretofore known is that we first heat the raw charging stock to the desired degree, preferably 880 F. to 925 F. but not greater than 1000 F., and then immediately transfer the saine to a well-insulated coking chamber, retaining the necessary heat to effect coking, without the application of additional heat to the coking chamber. The entire operation is carried on at sub.- stantially atmospheric pressure or a pressure just enough above atnios heric to force the vapors and fixed gases tnough the vapor take-off.

In practicing our improved process we have found that the ap lication of proper quantities of steam or ot 1er inert fluid such as natural gas, oil refinery gas or flue gas, at the desired point in the pipe still, while the residuum is under heat treatment, materially assists the operation. By its presence, the steam produces a partial pressure effect or a reduction of vapor pressure, thus increasing the vaporization of the residuum being treated and assisting the super-heat applied, to effect cokng, thereby making it possible to operate at lower temperatures and with less superheat applied to the residuum. Furthermore, the steam increases the velocity of said residuum passing through the coils. y

With the above and other objects in viev:r which will appear as the description proceeds, our invention consists in the novel features herein set forth, illustrated in the accompanying drawing and more particularly pointed out in the appended claims.

The drawing illustrates diagrammatically one form of apparatus which may be employed in carryinrr out our process, parts of said apparatus being shown in elevation andV parts in section.

In the drawing, 1 represents a furnace heated by a burner 2 or any suitable means, and in which are provided a series of pipe coils 3 and 3a. 4 represents a pipe line leading from the source of fuel oil or residuum 5 and connected to the inlet end 6 of the coils 3, a. suitable pump 7 being installed in said pipe line 4 for forcing the material to be treated into the coil. 8 and 9 designate well insulated coking chambers connected to the discharge end 10 of the coil 3a by branch lines 8a and 9a respectively, leading from a well insulated discharge line or conduit 11 for conveying the vapors and liquids from said coil 3a.

At a suitable point anterior to the coil 3a we provide a steam inlet 12 whereby steam is injected into the heated coil during the passage of the residuuni therethrough. The steam is preferably introduced into the coil at a point anterior to which no coke is likely to form in the coil.

In the upper portion of the coking chambers 8 and 9 We provide vapor take-off pipes 13 leading to a condensing coil 14 which in turn is directly connected to a suitable receptacle 15 in which the condensed liquids are collected, any uncondensed vapors or permanent gases entering the receptacle 15, being removed therefrom by any suitable means, not shown.

In our present construction the heating coil consists of 90 tubes, of three inch inside diameter, four inch outside diameter by 24 feet long, the total coil length including return bends being about 2230 feet, with approximately 2010 feet of tubing exposed to the lire, a preheating bank 3 and a final heating bank 3, The tubes are arranged in two banks of 45 tubes each. The charging stock enters the upper or preheating bank in a counterilow direction to the ascending flue gases which have been cooled by passing around the second or lower bank 3a. The charging stock then descends to the lower or final heating bank by means of the insulated connecting pipe 3b outside the furnace, and ascends in said second bank 3SL from its lower extremity in a direction parallel to the travel of the flue gases. The coking chambers 8 and 9 are heavily insulated, horizontal, cylindrical tanks 8 feet in diameter by 25 in length.

A typical o eration of our improved process was as fol ows:

Suitable charging stock such as fuel oil o'r petroleum residuum of 3.9 A. P. I. gravity, for example, from either crude oil stills or cracking stills was forced by the pump 7 into the heated coil 3 at the rate of approximately 43 barrels an hour', and was preheated to a temperature preferably in excess of 400 Fu during its passage through said coil. From the coil 3 the preheated oil flowed to the main heating coil 3'L where it was heated to a temperature ranging from 885 F. to 905 F.

Steam, at the rate of about 429 pounds per hour was continuously injected at 12 anterior to the final heating coil, into the residuuni passing through the said coil 3a, the quantity of steam added varying at times, to suit conditions.

'lhe mixture of steam, vapors and unvaporized material was conveyed by the relatively short-Well-insulated transfer line ll to one of the insulated receivers 8 or 9, sulicient heat being impounded in the residuum during its passage through the coil, so that, when it Was discharged from said coil into the coking chamber, there was a substantially complete vaporization of the volatile content. Due to the size of the chamber, the material was retained therein for a sutlicient length of time to utilize the heat umts iinpounded in the material to cause the deposition of a relatively large amount of coke in said chamber. conveyed from the coking chamber to a condenser 14 through the medium of the vapor take-oil' pipe 13, leaving the coke in the chamber 8 or 9.

By employing a plurality of coking chambers it will be seen that we are enabled to operate a continuous process, with a continthe coils 3 and 3'* at approximately 110 lbs.

per square inch pressure, or a pressure below that of the injected steam at its point of injection for obvious reasons, the only function of pressure in this process being to force the charging stock through the apparatus. Our process is distinguished from pressure processes in that in the former, where 110 lbs. pressure is employed asa pressure force, said pressure is merely pump pressure and is gauged at the inlet end, while in the latter a pressure is maintained throughout the entire system and is gauged at the discharge end. The pressure at the discharge end of coil 3a in our process should not exceed 50 pounds per square inch for satisfactory operation.

In our process during a run of 12 hours, 521 barrels of residuum of 3.9 A. P. I. gravity was treated, out of which 44,739 lbs. or 23 per cent by weight'of coke was produced, 72.4 per cent of distillate, and 4.6 per cent loss in uncondensable gases. The temperature maintained in the pipe still ranged from 885 F. to 905 F. at the outlet, and the steam injected amounted to approximately 5150 The distillate was vuous feed of raw material anda continuous los ilu

ian

pounds. The pressure maintained at the inlet of the coil was 125 lbs., and at the discharge end of coil 3 it did not exceed 50 pounds While the pressure in the coking chambers was about 3 lbs. gauge.

An analysis of the coke produced showed:

` Percent Volatile matter 13.24 Fixed carbon 81.78 'ish 4.98

B. t. u 13,853 per pound Sulphur` 1.229 per cent While We have described the above apparatus, operation and run in detail, they are given merely as examples, and obviously other' suitable apparatus for accomplishing the desired result may be employed. For example, it may be desirable to utilize the spent flue gases from the furnace to offset radiation in the coking chambers, by passing said flue gases underneath and around said chambers on their way to the stack. These flue gases are purely an additional insulating medium for further guarding against the dissipation of the heat impounded in the material discharged into the coking chambers and are not to be considered as additional external heat, the heat from said gases being insuiiicient to in any way effect the reaction in the chambers.

It will be noted that in actual practice the raw charge may be preheated by means of a heat exchanger which transfers the heat from the hot vapors leaving the coking chambers, to the raw charge before it enters the coil 3, thus eliminating the preheating coil 3.

In practicing our process, the temperatures, pressures and proportions may also be Varied to suit conditions, the temperature of the pipe still being controlled and varied according to the character of the raw charge to be treated.

From the foregoing it will be seen that our improved process possesses all o f the advantages of the standard coking still o eration with very few, if any, of 1ts disa van' tages. As may be readily seen, an installation of apparatus suitable for conductmg our process can be made in which the investment is small, the capacity high with the maxi` mum furnace etliciency, the maintenance cost far below the Ordinar and the cleaning costsmuch less than t e standard coking still operation.

The result obtained by our process, and not obtained in any of those with which we are familiar is that through the use of superheat, aided by the injection ofsteam, we are able to reduce the volatile matter remaining in the coke to a minimumthus producing a high quality coke, directly comparable with other petroleum cokes and for which there are established markets.

Furthermore, our process affords almost unlimiting flexibility in charging stock and the character of the product produced, as by varying the coil outlet temperature we are able to obtain coke of any desired volatile content. It will also be noted that We have experienced no ditticulty due to coke forming in the coil.

By such terms as heavy residuum hydrocarbon oil and petroleum residuum, in the claims, we mean such charging stock as fuel oil or petroleum residuum from either crude oil stills or cracking stills.

From the above it is believed that our process may be readily understood by those skilled in the art without further descrip tion, it being borne in mind that numerous changes may be made in the details of construction and operation Without departing from the spirit of the invention as set forth in the following claims.

What we claim and desire to secure by Letters Patent is: `1. The process of treating heavy residuum hydrocarbon oil for the production of an optimum yield of coke, which comprises preheatin said oil and forcing the same throug an elongated passageway of restricted cross sectional area, heating said oil during its flow through said passageway, injccting a suitable heated gaseous fluid which 1s chemically inert, into said oil at a point anterior to the last named heating step, transferring the resulting mixture without any substantial loss of heat, from said passageway to an expansion zone, and maintaining the mixture in said zone for a sufficient length of time to utilize the heat units impounded therein, to cause the deposition of an optimum amount of coke from said mixture, said oil being heated in said passageway to temperatures insufficient to materially crack the oil during its flow through said passageway, but suiiicient to cause a substantially complete vaporization of the volatile content of said oil at the outlet of said passageway the pressure on said mixture at the outlet of said passageway not exceeding 50 pounds per square inch.

2. The process of treating heavy residuum hydrocarbon oil for the production of an optimum yield of coke, which comprises preheatin said oil and forcing the same throug 1 an elongated 'passageway of restricted cross sectional area, heating said oil during its flow through said passageway, to

temperatures from 880 F. to 925 F., injecting a suitable heated Cgaseous iiuid which is chemically inert at sai temperatures, into said oil at a point anterior to said last named heating step, transferring the 'resulting mixture without any materlal cracking having taken place and without any substantial loss of heat but substantially in vapor form, from said passageway to an expansion zone, and maintaining the mixture in said zone for a sufficient length of time to utilize the heat units impounded therein, to cause the deposition of an optimum amount of coke from said mixture, the pressure on said mixture at the outlet of said passageway not exceeding 50 pounds per square inch and the pressure in said expansion zone being only slightly in excess of atmospheric pressure.

3. The process of treating a heavy-petroleum residuum from a cracking still or the like for the production of an optimum yield of coke, which comprises preheating said residuum and forcing the same through an elongated passageway of restricted cross sectional area, heating said residuum during its flow through said passageway, to temperatures from 880 F. to 925 F., maintaining a pressure at the outlet of said passageway not exceeding 50 pounds per square inch, injecting a suitable heated gaseous fluid which is chemically inert at said temperatures, into said residuum at a point anterior to said last named heating step, transferring the resulting mixture without any material cracking having taken place and without any substan` tial loss of heat, from said passageway to an expansion zone, wherein a substantially complete vaporization of the volatile content of the mixture occurs, without the addition of further external heat, and maintaining the mixture in said zone for a sufficient length of time to utilize the heat units impounded therein, to cause the deposition of an optimum amount of coke from said mixtu; e, the pressure in said expansion zone not greatly exceeding atmospheric pressure.

4. The process of treating a heavy petroleum residuum from a cracking still or the like for the production of an optimum yield of coke, which comprises preheating said residuum and forcing the same through an elongated passageway of restricted cross sectional area, heating said residuum during its flow through said passageway, to temperatures from 880 F. to 925 F., maintaining a pressure at the outlet of said passageway not exceeding 50 pounds per square inch, injecting a suitable heated gaseous fluid which is chemically inert at said temperatures, into said residuum at appoint anterior to said last named heating step, transferring the resulting mixture without any material cracking having taken place and without any substantial loss of heat, from said passageway to an expansion zone, wherein a substantially complete vaporization of the volatile content of the mixture occurs, without the addition of further external heat, maintaining the 'mixture in said zone for a sufficient length of time to utilize the heat units impounded therein, to cause' the deposition of an optimum amount of coke from said mixture, the pressure in said expansion zone not greatly exceeding atmospheric pressure, and withdrawing and condensing the vapors from said zone.

5. The process of treating heavy residuum hydrocarbon oil from a cracking still or the like for the production of an optimum yield of coke, which comprises preheating such residuum and forcing the sarne through an elongated passageway of restricted cross sectional area, heating said residuum during its flow through said passageway to temperatures from 880 F. to 925 F., injecting steam into said residuum as the latter travels through said passageway, immediately transferring the resulting mixture without any substantial loss of. heat, from said passageway to an expansion zone, wherein a substantially complete vaporization of the volatile content of the mixture occurs, without the addition of further external heat, and maintaining the mixture in said zone for a sufficient length of time to utilize the heat units impounded therein, to cause the deposition of a relatively large amount of coke from said mixture, the pressure at the outlet of said passageway being super-atmospheric but not exceeding 50 pounds per square inch and the pressure in said expansion zone not materially exceeding atmospheric pressure.

6. The process of treating heavy residuum oil for the production of an optimum yield of coke, which comprises forcing suchv oil through an elongated passageway of restricted cross sectional area, heating said oil during its iow through said passageway, to temperatures from 880 F. to 925 F., injecting a suitable gaseous fluid which is chemically inert at said temperatures, into said oil-at an intermediate point in said passageway after said oil has been preheated in said passageway, transferring the resulting mixture without any material cracking having taken place and without any substantial loss of heat, from said passageway to an expansion zone, where a substantially complete Vaporization of the volatile content of the mixture occurs, without the addition of further external heat, maintaining the mixture in said zone for a sufficient length of time to utilize the heat units impounded therein, to cause the deposition of an optimum amount of coke from said mixture, and withdrawing and condensing the vapors from said zone, the pressure at the outlet of said passageway not exceeding 50 pounds per square inch and the pressure in said expansionzone not materially exceeding atmospheric pressure.

In testimony whereof we aix our signatures.

KENNETH J. SMITH. HOWARD V. SMITH. 

